In this Chapter I begin by discussing the late nineteenth-century and early twentieth-century constitutional climate in which the Canadian and Australian federations were created. At that time, thinking regarding sovereignty was dominated by the absolutist version favoured by Austin and, later, Dicey. According to this version, the Westminster Parliament could certainly constitute a federation in Canada and later Australia. But anything that the Westminster Parliament enacted could, in strict law, be altered or undone at a later time. The period from the Balfour Declaration and Statute of Westminster 1931 to the 1980s saw considerable evolution in understandings of sovereignty, to the point where it was assumed, at least by Canadian and Australian courts and commentators, that the Westminster Parliament could limit itself entirely, where their legal systems were concerned, and that such limitations were permanent, that is, irreversible. So viewed from a Canadian and Australian perspective, the Westminster Parliament not only created federal constitutions but also put them beyond the reach of that sovereign Parliament.

I then consider in the form of a series of propositions whether that which the Westminster Parliament created for Canada, Australia and other Commonwealth federations could be created for the United Kingdom itself. I conclude that it is possible, and were it to happen, it should involve legislation by Parliament indicating a clear intention to limit itself in the creation of a federation, together with a process – widespread consultation, a referendum and conspicuous respect for the best-learned lessons regarding principles such as constitutionalism, the rule of law and democracy – which would reassure officials that the change in the ultimate rule of the legal system was right and proper, and appropriate.